From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E833C433F1 for ; Mon, 27 Jul 2020 14:14:23 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DCEC32073E for ; Mon, 27 Jul 2020 14:14:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="rKrr+Rda" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DCEC32073E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 740C41699; Mon, 27 Jul 2020 16:13:31 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 740C41699 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1595859261; bh=NcvzRFn08FMk+XpEsMYgYvqc7TT0oEUoNBJzdA6q7Og=; h=Subject:To:References:From:Date:In-Reply-To:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=rKrr+RdaiKxi4Tb4MyaDfZu25Ct3PM3fNAupqAYeJds2WTBK/51sMtBo90pu5Z1DU oqRF6VaJli0TNqwg76DDmizvflOICrm2MF++P/4gI9lzrg2t993dM4VtnR3aKbqUFb xJqmzUx4L4l0nP1WUqoc4PQ/zp2RjzeFPty/eI0Q= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id F370CF8013C; Mon, 27 Jul 2020 16:13:30 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 1153FF80171; Mon, 27 Jul 2020 16:13:29 +0200 (CEST) Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 8F274F800DE for ; Mon, 27 Jul 2020 16:13:18 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 8F274F800DE IronPort-SDR: XeDKRgkbqR+EmlSndBLkMcARmCVg+koFolNVN+S6OKbbfsPvCfuri/tlk4WLVXyBCzmyWrW1hq OwkKwQTgSLjQ== X-IronPort-AV: E=McAfee;i="6000,8403,9694"; a="212543818" X-IronPort-AV: E=Sophos;i="5.75,402,1589266800"; d="scan'208";a="212543818" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jul 2020 07:13:15 -0700 IronPort-SDR: JzN8m632tAb7YYMiQBLQMIPjhJWU8qI8y81PGQHnF2GJlRZiyLW5mcBtzgCHp3ASKp6cIpegVD Ax1KhNirjKww== X-IronPort-AV: E=Sophos;i="5.75,402,1589266800"; d="scan'208";a="464072084" Received: from pdewan-mobl1.amr.corp.intel.com (HELO [10.255.228.220]) ([10.255.228.220]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jul 2020 07:13:15 -0700 Subject: Re: [PATCH] ASoC: core: use less strict tests for dailink capabilities To: Jerome Brunet , alsa-devel@alsa-project.org References: <20200723180533.220312-1-pierre-louis.bossart@linux.intel.com> <1jlfj98gb4.fsf@starbuckisacylon.baylibre.com> <576823fb-a8a8-1f74-b7e2-d33b734022a7@linux.intel.com> <1jk0yp8fb7.fsf@starbuckisacylon.baylibre.com> From: Pierre-Louis Bossart Message-ID: Date: Mon, 27 Jul 2020 09:13:13 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1jk0yp8fb7.fsf@starbuckisacylon.baylibre.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Cc: tiwai@suse.de, broonie@kernel.org X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On 7/27/20 4:42 AM, Jerome Brunet wrote: > > On Fri 24 Jul 2020 at 21:05, Pierre-Louis Bossart wrote: > >>> Again, this is changing the original meaning of the flag from "playback >>> allowed" to "playback required". >>> >>> This patch (or the orignal) does not explain why this change of meaning >>> is necessary ? The point I was making here [0] still stands. >>> >>> If your evil plan is to get rid of 2 of the 4 flags, why go through the >>> trouble of the changing the meaning and effect of one them ? >> >> My intent was to have a non-ambiguous definition. > > I still fail to understand how it was ambiguous and how throwing an > error for something that used to work well so far is making things better. > > Maybe there could be have been a better name for it, but what it did was > clear. > > The flag is even (briefly) documented: > /* DPCM capture and Playback support */ > unsigned int dpcm_capture:1; > unsigned int dpcm_playback:1; > > "Support" means the dai_link supports it, not that it is required for it > work. This is what was implemented. > >> >> I don't know 'playback allowed' means. What is the point of using this flag >> if it may or may not accurately describe what is actually implemented? And >> how can we converge the use of flags since in the contrary 'playback_only' >> is actually a clear indication of what the link does. We've got to align on >> the semantics, and I really don't see the point of watering-down >> definitions. When things are optional or poorly defined, the confusion >> continues. > > The problem is that commit b73287f0b074 ("ASoC: soc-pcm: dpcm: fix > playback/capture checks") has changed the semantic: > * without actually warning that it was doing so in the commit description > * breaking things for other who relied on the previous semantics > > Previous semantics of the flag allowed to disable a stream direction on > a link which could have otherwise had it working, if the stream had it. > It added information/control on the link at least. > > New flag semantics forces the flag and stream capabilities to be somehow > aligned. This is not clearing the confusion, this is redundant > information. How is this helping the framework or the users ? > >> >> WFIW, my 'evil' plan was to rename 'dpcm_playback' as 'can_playback' (same >> for capture) and replace 'playback_only' by 'can_playback = 1; can_capture >> = 0'. So this first step was really to align them on the expected behavior >> and minimal requirements. > > IMO the previous flag semantics was inverted yes, but aligned: > > playback_only = 1 was the same as dpcm_capture = 0 > capture_only = 1 was the same as dpcm_playback = 0 > > Having both *_only set does not make sense for a stream, same as having > none of dpcm_* > > Having none of *_only flag means there is no restriction on the stream, > same as having both dpcm_* set. > > This seems aligned to me. Makes no sense to me to have information that's useless. What does 'no restrictions' on a stream mean? 'anything goes' is not a scalable design principle.